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VGA to X-Y-Z scope converter

2016-01-17 10:20  
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This is fun project I found onJon’s antique radiosweb-page. He has managed to convert VGA output signal from PC to X Y X oscilloscope signal. Converting VGA RGB signal to synchronized oscilloscope input signal is pretty easy because VGA has two sync signals separate from RGB signals. Look at pin-out of VGA cable:


Sync signals makes things much easier as there is no need for additional sync signal generators a€“ thus circuit becomes pretty simple without any programmable components:


The sync signals taken from VGA cable triggers sweep tooth signal (555 timer) generators. These generators generates ram signals for oscilloscope, that enable creation of raster pattern. The vertical generator frequency is around 75Hz and horizontal about 35kHz is used as horizontal sync pulses. Output sync (75Hz) is fed to oscilloscope Y-axis and and 35kHz sync signal is fed to X-axis of oscilloscope. The circuit is ready for 800 x 600 at 75Hz refresh rate. For different configurations you might need to adjust horizontal and vertical sync 555timers RC circuits.

RGB signal is converted to monochrome signal and fed to Z-axis of oscilloscope as intensity.


Inside the box:


Be sure that you turn PC before switching oscilloscope ON otherwise without PC sync signal you will get bright dot on Oscilloscope screen what can burn the phosphor. When turning off a€“ turn oscilloscope first before turning off PC.

Circuit is sensitive to voltage swings. Be sure that you have stabile 5V.

PC desktop image:


The image on oscilloscope:


References: Jon’s antique radios.

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